In vehicles, for example in buses and rail vehicles, it is customary to equip the doors in the closing region with an elastic section which protects trapped persons or objects against injury or damage. Methods have also been proposed which are suitable for detecting a person trapped in the door or a trapped object and triggering a suitable vehicle reaction. A suitable reaction is, for example in addition to the immediate opening of the door, to signal to the driver of the vehicle or even to disconnect the power supply to the drive.
In particular, a device in which the elastic section is hollow and the signal runs along in the cavity which is formed in this way is suitable for carrying out such a method. Generally, a transmitter and a receiver at opposite ends of the cavity are used for this. Suitable signals are ultrasonic or electromagnetic waves, in particular light.
It is also known to arrange a strip connector in the elastic section, which connector has two electrically conductive strips which can move with respect to one another. If a person or an object is trapped in the door, these strips touch one another generating a signal which indicates that trapping has occurred. In such a device, a comparison does not however take place between a received signal and a setpoint value.
According to the applicable standardization, all the methods and devices for detecting an object which is trapped in a door are to be capable of detecting objects with a cross section of 30 mm×60 mm.
However, it may be the case that relatively thin objects, for example an item of clothing or a belt, are trapped, which is very hazardous, in particular if the affected person is located outside the vehicle. If the vehicle is an underground train which is operated without a driver, the risk for persons is particularly high as there is no longer any monitoring of the platform by staff.